This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
The invention relates generally to welding systems and, more particularly, to torches having a wire fed to a contact tip.
Existing welding torches, such as metal inert gas (MIG) torches, pass a welding wire and a shielding gas through a neck (e.g., a gooseneck) to a torch head having a nozzle, diffuser, and contact tip. At the torch head, the contact tip transfers energy (e.g., current) to the welding wire, and an arc forms between the welding wire and a work piece. The arc then melts the welding wire to form a weld on the work piece. In addition, the shielding gas protects the arc and the weld during the process, for example, to avoid oxidation and other problems.
In many welding systems, a wire feeder draws the welding wire from its package and feeds it through a torch. The welding wire, when drawn out of the package, may have various curvatures (e.g., cast and helix), which depends on the manufacturing processes such as cold drawing, heat treatment, coiling, the geometry of the package, and so forth. The curvature can cause the welding wire to bind, jam, or flip within the torch. For example, the welding wire may curve in a helical manner (e.g., like a coil spring) when pulled from the spool. By further example, the welding wire may curve in a sinusoidal manner (e.g., like a snake) when pulled from the spool. In either case, the curvature can cause problems within the torch. Recently, wire manufacturers have produced wire for automatic and robotic applications that maintains a substantially straight geometry when pulled from the package. In other words, the welding wire curves in a sinusoidal manner with a radius of 60 inches or more, rather than a traditional circular case with a radius of 20 to 30 inches. Although this relatively straight geometry reduces some problems with binding, jamming, or flipping within the torch, it also causes problems with inconsistent contact between the contact tip and the welding wire.
At the torch head, the torch transfers energy (e.g., current) from the contact tip to the welding wire. However, the energy transfer can depend largely on the contact between the welding wire and the internal passage through the contact tip. If the welding wire does not adequately contact the internal passage of the contact tip, then more energy is consumed at the interface between the contact tip and the welding wire, and arcing can occur inside the contact tip leading to undesirable arc damage, deposits, and so forth. In turn, the contact tip can prematurely wear out and cease to transfer sufficient energy (e.g., current) to the welding wire, thereby decreasing energy transfer between the welding wire and the work piece. The premature wear can also cause large fluctuations of the welding current and arc stability. If insufficient energy is transferred to the weld location, then the welding wire may not melt to form the weld and/or the weld may not have the desirable characteristics leading to subsequent failure.
In summary, welding wire having a relatively straight geometry when pulled from a package can result in reduced contact between the welding wire and the internal passage of the contact tip. As a result, the welding wire itself can cause premature wear and failure of the contact tip.